U.S. Pat. No. 4,400,340 to D. W. Klosiewicz, incorporated by reference herein, discloses a method for making a thermoset polymer of dicyclopentadiene (DCPD) with a metathesis catalyst system using a Reaction Injection Molding (RIM) process.
In the typical RIM process, at least two reactant streams, at least one of which contains DCPD and each containing one part of a two-part catalyst system, are combined in a mixhead, and this mixture is then injected into a mold where polymerization occurs, forming a thermoset polymer. Being a hydrocarbon, the thermoset polymer has intrinsic flammability and will burn continuously when ignited under Standard UL-94 test procedures.
Until now the prior art has not taught how to make flame retardant poly(DCPD) by a RIM process. Although there exist liquid flame retardant additives for thermoset polymers, they are unsuitable in poly(DCPD) RIM process. To impart effective flame retardancy, they must be used in amounts that can delay or inhibit polymerization.
Solid flame retardants are also known. However, their compatibility in DCPD polymerization using metathesis catalysts was questionable, i.e., some solid flame retardants react with the catalyst thereby inhibiting or preventing polymerization. Also, it was unknown if a compatible solid flame retardant, once found, would also be capable of being incorporated into RIM processing, i.e., would it only require the addition of a sufficiently low enough amount of solids so as not to interfere with the fluid mechanics of RIM processing?
An objective of the present invention is to develop RIM compatible solid flame retardants that are chemically compatible with the metathesis catalyst system, i.e., retardants that will not impede polymerization of dicyclopentadiene, and yet be capable of being dispersed in dicyclopentadiene to form a pumpable slurry.